For a ksym to be safely dereferenced and accessed, its type defined in bpf program should basically match its type defined in kernel. Implement a help function for a quick matching, which is used by libbpf when resolving the kernel btf_id of a ksym.
Signed-off-by: Hao Luo <[email protected]> --- tools/lib/bpf/btf.c | 171 ++++++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/btf.h | 2 + 2 files changed, 173 insertions(+) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index a3d259e614b0..2ff31f244d7a 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1005,6 +1005,177 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name, return 0; } +/* + * Basic type check for ksym support. Only checks type kind and resolved size. + */ +static inline +bool btf_ksym_equal_type(const struct btf *ba, __u32 type_a, + const struct btf *bb, __u32 type_b) +{ + const struct btf_type *ta, *tb; + + ta = btf__type_by_id(ba, type_a); + tb = btf__type_by_id(bb, type_b); + + /* compare type kind */ + if (btf_kind(ta) != btf_kind(tb)) + return false; + + /* compare resolved type size */ + return btf__resolve_size(ba, type_a) == btf__resolve_size(bb, type_b); +} + +/* + * Match a ksym's type defined in bpf programs against its type encoded in + * kernel btf. + */ +bool btf_ksym_type_match(const struct btf *ba, __u32 id_a, + const struct btf *bb, __u32 id_b) +{ + const struct btf_type *ta = btf__type_by_id(ba, id_a); + const struct btf_type *tb = btf__type_by_id(bb, id_b); + int i; + + /* compare type kind */ + if (btf_kind(ta) != btf_kind(tb)) { + pr_warn("%s:mismatched type kind (%d v.s. %d).\n", + __func__, btf_kind(ta), btf_kind(tb)); + return false; + } + + switch (btf_kind(ta)) { + case BTF_KIND_INT: { /* compare size and encoding */ + __u32 ea, eb; + + if (ta->size != tb->size) { + pr_warn("%s:INT size mismatch, (%u v.s. %u)\n", + __func__, ta->size, tb->size); + return false; + } + ea = *(__u32 *)(ta + 1); + eb = *(__u32 *)(tb + 1); + if (ea != eb) { + pr_warn("%s:INT encoding mismatch (%u v.s. %u)\n", + __func__, ea, eb); + return false; + } + break; + } + case BTF_KIND_ARRAY: { /* compare type and number of elements */ + const struct btf_array *ea, *eb; + + ea = btf_array(ta); + eb = btf_array(tb); + if (!btf_ksym_equal_type(ba, ea->type, bb, eb->type)) { + pr_warn("%s:ARRAY elem type mismatch.\n", __func__); + return false; + } + if (ea->nelems != eb->nelems) { + pr_warn("%s:ARRAY nelems mismatch (%d v.s. %d)\n", + __func__, ea->nelems, eb->nelems); + return false; + } + break; + } + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: { /* compare size, vlen and member offset, name */ + const struct btf_member *ma, *mb; + + if (ta->size != tb->size) { + pr_warn("%s:STRUCT size mismatch, (%u v.s. %u)\n", + __func__, ta->size, tb->size); + return false; + } + if (btf_vlen(ta) != btf_vlen(tb)) { + pr_warn("%s:STRUCT vlen mismatch, (%u v.s. %u)\n", + __func__, btf_vlen(ta), btf_vlen(tb)); + return false; + } + + ma = btf_members(ta); + mb = btf_members(tb); + for (i = 0; i < btf_vlen(ta); i++, ma++, mb++) { + const char *na, *nb; + + if (ma->offset != mb->offset) { + pr_warn("%s:STRUCT field offset mismatch, (%u v.s. %u)\n", + __func__, ma->offset, mb->offset); + return false; + } + na = btf__name_by_offset(ba, ma->name_off); + nb = btf__name_by_offset(bb, mb->name_off); + if (strcmp(na, nb)) { + pr_warn("%s:STRUCT field name mismatch, (%s v.s. %s)\n", + __func__, na, nb); + return false; + } + } + break; + } + case BTF_KIND_ENUM: { /* compare vlen and member value, name */ + const struct btf_enum *ma, *mb; + + if (btf_vlen(ta) != btf_vlen(tb)) { + pr_warn("%s:ENUM vlen mismatch, (%u v.s. %u)\n", + __func__, btf_vlen(ta), btf_vlen(tb)); + return false; + } + + ma = btf_enum(ta); + mb = btf_enum(tb); + for (i = 0; i < btf_vlen(ta); i++, ma++, mb++) { + if (ma->val != mb->val) { + pr_warn("%s:ENUM val mismatch, (%u v.s. %u)\n", + __func__, ma->val, mb->val); + return false; + } + } + break; + } + case BTF_KIND_PTR: { /* naive compare of ref type for PTR */ + if (!btf_ksym_equal_type(ba, ta->type, bb, tb->type)) { + pr_warn("%s:PTR ref type mismatch.\n", __func__); + return false; + } + break; + } + case BTF_KIND_FUNC_PROTO: { /* naive compare of vlen and param types */ + const struct btf_param *pa, *pb; + + if (btf_vlen(ta) != btf_vlen(tb)) { + pr_warn("%s:FUNC_PROTO vlen mismatch, (%u v.s. %u)\n", + __func__, btf_vlen(ta), btf_vlen(tb)); + return false; + } + + pa = btf_params(ta); + pb = btf_params(tb); + for (i = 0; i < btf_vlen(ta); i++, pa++, pb++) { + if (!btf_ksym_equal_type(ba, pa->type, bb, pb->type)) { + pr_warn("%s:FUNC_PROTO params type mismatch.\n", + __func__); + return false; + } + } + break; + } + case BTF_KIND_FUNC: + case BTF_KIND_CONST: + case BTF_KIND_VOLATILE: + case BTF_KIND_RESTRICT: + case BTF_KIND_TYPEDEF: + case BTF_KIND_VAR: + case BTF_KIND_DATASEC: + pr_warn("unexpected type for matching ksym types.\n"); + return false; + default: + pr_warn("unsupported btf types.\n"); + return false; + } + + return true; +} + struct btf_ext_sec_setup_param { __u32 off; __u32 len; diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 91f0ad0e0325..5ef220e52485 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -52,6 +52,8 @@ LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name, __u32 expected_key_size, __u32 expected_value_size, __u32 *key_type_id, __u32 *value_type_id); +LIBBPF_API bool btf_ksym_type_match(const struct btf *ba, __u32 id_a, + const struct btf *bb, __u32 id_b); LIBBPF_API struct btf_ext *btf_ext__new(__u8 *data, __u32 size); LIBBPF_API void btf_ext__free(struct btf_ext *btf_ext); -- 2.28.0.220.ged08abb693-goog
